Biochemical versatility and stress modulation: UGTs in the Fabaceae family

The Fabaceae-specific review highlights the structural, functional, and phylogenetic diversity of UGTs, revealing clade-specific glycosylation mechanisms and novel sugar conjugations that contribute to legume adaptability. These insights offer promising avenues for metabolic engineering and stress-resilient crop development. UDP-glycosyltransferases (UGTs) are the biocatalysts modifying small molecules through glycosylation to enhance their solubility, stability, and bioactivity. They alter the physiology of the plant thereby enhancing adaptability and resilience in plants. In the last five years, several comprehensive reviews highlighting their classification, functional characterization, substrate recognition mechanism, ginsenoside biosynthesis, xenobiotic resistance, and possible applications in agriculture have been published. Reviews have also discussed and analyzed structure and functions of specific UGTs catalyzing flavonoid and medicinal terpenoids; however, resources on UGTs specific to Fabaceae family have not been deliberated. The Fabaceae family houses diverse agronomically important plants which are the major source of plant-based proteins, edible oil, medicines, natural nitrogen fixers, dyes, and several other usages. Published reports advocate UGTs from legumes contribute to chemical diversity by glycosylating flavonoids, terpenoids, and phytohormones, often through O-, C-linkage, and rare sugar conjugations such as arabinosylation and xylosylation. This review integrates phylogenetic analysis, motif architecture, and functional data from characterized UGTs mined from the legume family, and their high-throughput screening platforms for functionality assignment. The review classifies reported characterized UGTs from Fabaceae into eight major clades (A, D, E, F, G, L, M, and R), each associated with distinct enzymatic functions. Group E (UGT71/72/88) primarily mediated 3-O and 7-O flavonoid glycosylation, while Group D (UGT73) showed the broadest substrate acceptability range from phytohormones to secondary metabolites. Novel sugar conjugation was also seen suggesting evolutionary innovation within the legumes and their potential utility in metabolic engineering and crop improvement.